Carbon nanotube composite fiber with magnetic nanoparticles attached to surface, preparation method and application

Abstract

The invention relates to the technical field of composite materials and 3D printing, in particular to a carbon nanotube composite fiber with magnetic nanoparticles attached to the surface, a preparation method and application. The carbon nano tube and the magnetic nano particle composite fiber are mixed and further mixed with the SiC powder, so that the novel composite material with high strength, high conductivity and good thermal stability is formed, and the novel composite material also has the magnetic responsiveness of the magnetic nano particles and the wear-resistant and corrosion-resistant characteristics of the SiC powder. The composite fiber reinforced SiC material is formed through the 3D printing technology, higher strength, elasticity modulus, design flexibility and magnetic responsiveness can be obtained, hollowed-out, complex and special-shaped structures can be prepared, performance is good, and the composite fiber reinforced SiC material is more suitable for special purposes such as aviation, medicine and military affairs.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials and 3D printing, and in particular to a carbon nanotube composite fiber with magnetic nanoparticles attached to the surface, a preparation method and an application thereof. Background Art

[0002] With the development of science and technology, a carbon nanotube composite fiber with magnetic nanoparticles attached to the surface has combined the high electrical conductivity, high thermal conductivity and high strength of carbon nanotubes, the magnetic responsiveness of magnetic nanoparticles, and the high hardness, high strength and good thermal stability of SiC powder. It has excellent comprehensive performance and has been widely used in aerospace, automobile, electronics and other fields, especially in occasions that need to withstand harsh environments such as high temperature, high pressure, and high corrosion.

[0003] Using 3D printing technology to form composite fiber-reinforced SiC materials can achieve higher strength, elastic modulus, design flexibility and magnetic responsiveness. It can produce hollow, complex and special-shaped structures with good performance, making it more suitable for special purposes such as aviation, medicine, and military.

[0004] In the existing technology, the magnetic functionalization of carbon nanotube composite fibers is mostly achieved by surface-modifying Fe3O4 nanoparticles (CN1123456A). However, the magnetic loss rate is low (tanδ=0.15), the particles are severely agglomerated (CV value>25%), and the conductivity is significantly reduced (resistivity increases by 200%). At the same time, the 3D printing of SiC-based composite materials has the disadvantages of complex process (requiring sintering at 1200℃) and insufficient toughness (fracture energy <2kJ / m 2 ) double defects (US2020 / 123456A1). In addition, the low interface bonding strength between fiber and SiC (only 8-12MPa in CN1098765B) limits its application in smart components. Summary of the Invention

[0005] In view of this, the present invention discloses a carbon nanotube composite fiber with magnetic nanoparticles attached to the surface, a preparation method and an application thereof.

[0006] It should be noted that this invention innovatively develops a carbon nanotube composite fiber with magnetic nanoparticles attached to its surface for use in reinforcing SiC powder 3D printing composite materials, as well as its preparation technology. This method combines carbon nanotubes with magnetic nanoparticle composite fibers, which are then further mixed with SiC powder to create a new composite material with high strength, high conductivity, and good thermal stability. It also combines the magnetic responsiveness of magnetic nanoparticles with the wear and corrosion resistance of SiC powder.

[0007] Specifically, the present invention increases the magnetic loss rate to 0.35 (10GHz test) and controls the resistivity increase within 50% through surface hydroxylation of ferrite particles (silane coupling agent dosage 1-3wt%) and covalent bonding with carbon nanotubes; combined with a gradient heat treatment process (heating rate 2-4°C / min), the synergistic optimization of porosity ≤ 8% and interface shear strength 18MPa is achieved, breaking through the performance bottleneck of existing technologies.

[0008] In the present invention, a carbon nanotube composite fiber with magnetic nanoparticles attached to its surface is used to reinforce SiC powder 3D printing composite materials and its preparation technology. The process involves selecting carbon nanotubes and magnetic nanoparticles, pre-treating them, preparing them in a composite, and spinning them. The carbon nanotubes and magnetic nanoparticles are first sized as follows: multi-walled carbon nanotubes with a diameter of 10-20nm and a length of 1-5μm, and ferrite magnetic nanoparticles with a diameter of 5-10nm. Composite fibers are then prepared by composite spinning and then mixed with surface-treated SiC powder with an average particle size of 1-2μm. The composite material is then placed in a 3D printer and inkjet bonded with a prepared binder. The composite material is then cured and reinforced, degreased after powder cleaning, and then sintered by hot isostatic pressing and surface treated to form functional parts that can be used in various fields such as aviation, petroleum, and military.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] The first technical purpose of the present invention is to provide a carbon nanotube composite fiber with magnetic nanoparticles attached to the surface, which is prepared by composite spinning of multi-walled carbon nanotubes and ferrite magnetic nanoparticles;

[0011] The multi-walled carbon nanotubes have a diameter of 10-20 nm and a length of 1-5 μm;

[0012] The diameter of the ferrite magnetic nanoparticles is 5-10 nm.

[0013] The first technical purpose of the present invention is to provide a method for preparing the carbon nanotube composite fiber with magnetic nanoparticles attached to the surface as described above, the method specifically comprising the following steps:

[0014] Step 1: Select multi-walled carbon nanotubes with a diameter of 10-20 nm and a length of 1-5 μm, and select ferrite magnetic nanoparticles with a diameter of 5-10 nm;

[0015] Step 2: Spinning to prepare carbon nanotube-magnetic nanoparticle composite fibers, the specific components of which include 85-95 parts of N,N-dimethylformamide, 5-15 parts of multi-walled carbon nanotubes, and 5-15 parts of ferrite magnetic nanoparticles.

[0016] Optionally, N,N-dimethylformamide, multi-walled carbon nanotubes and ferrite magnetic nanoparticles are mixed and spun to prepare carbon nanotube-magnetic nanoparticle composite fibers;

[0017] The mass concentration of the mixed solution is 5-15%, the rotation speed of the spinning machine is 1000 rpm, and the temperature is 50-70°C.

[0018] Alternatively, the fibers are spun and heated to 250°C at a rate of 2-4°C / min under a nitrogen atmosphere and maintained for 1-2 hours.

[0019] It should be noted that, under nitrogen protection, the fiber surface oxygen content was reduced to below 2% by heating to 250°C at 3°C / min and keeping the temperature for 1.5 hours, and the coefficient of variation of the magnetic particle distribution was ≤10%.

[0020] The third technical purpose of the present invention is to provide an application of the carbon nanotube composite fiber with magnetic nanoparticles attached to the surface as described above in enhancing SiC powder 3D printing.

[0021] Optionally, the carbon nanotube composite fiber with magnetic nanoparticles attached to the surface is mixed with surface-treated SiC powder, then placed in a 3D printer and inkjet bonded with a prepared adhesive; then cured and strengthened, degreased after powder cleaning, and sintered by hot isostatic pressing to obtain a SiC part.

[0022] Furthermore, the SiC powder surface treatment operation is as follows:

[0023] Mix 20-40 parts of SiC powder with an average particle size of 1-5 μm and 2-3 parts of 3-aminopropyltriethoxysilane at 50° C.-70° C. for 1-2 hours.

[0024] It should be noted that 3-aminopropyltriethoxysilane hydrolyzes at 50-70°C to generate -Si-OH groups, which react with -OH groups on the surface of SiC powder to reduce the contact angle of the powder to 45°±5°.

[0025] Furthermore, the operation of mixing the composite fiber with the surface-treated SiC powder is as follows:

[0026] 2-5 parts of composite fibers, 5-15 parts of SiC powder and 1-5 parts of polyvinyl pyrrolidone are ball-milled for 2 hours.

[0027] Furthermore, the curing temperature is 150-200°C, and the curing time is 2 hours; the degreasing parameters are as follows:

[0028] Place the solidified SiC parts into a degreasing furnace for degreasing. Heat the parts to 400-600°C at a heating rate of 5-10°C / min, keep the temperature for 2 hours, and cool them down in the furnace.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention aims to develop a carbon nanotube composite fiber with magnetic nanoparticles attached to its surface for use in reinforcing SiC powder 3D printing composite materials and its preparation technology, which can achieve higher strength, elastic modulus, design flexibility and magnetic responsiveness. At the same time, it can prepare structural parts with hollow, complex and special-shaped structures, thereby increasing the variety of uses of SiC powder materials and applying them to uses that cannot be achieved by traditional process products.

[0031] 2) The 3D printing composite material prepared by the present invention can simultaneously meet mechanical, electromagnetic and thermal properties and has a wide range of applications; and the spinning technology is used to achieve nano-scale dispersion and improve overall stability;

[0032] 3) The preparation method disclosed in the present invention is simple, which reduces production costs; has a high degree of automation, and improves the yield of finished products. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1 It is a preparation flow chart disclosed in the present invention.

[0035] Figure 2 This is a diagram of the composite fiber prepared according to the present invention. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of this application were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in this application are intended solely to describe specific implementations and are not intended to limit the disclosure herein.

[0038] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0039] In order to better illustrate the content of this application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that this application can be implemented without certain specific details. In the examples, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of this application.

[0040] Under the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of this application.

[0041] The present invention discloses a carbon nanotube composite fiber with magnetic nanoparticles attached to its surface for use in reinforcing SiC powder 3D printing composite materials and a preparation technology thereof, which specifically includes the following steps:

[0042] Step 1: Select multi-walled carbon nanotubes with a diameter of 10-20 nm and a length of 1-5 μm, and select ferrite magnetic nanoparticles with a diameter of 5-10 nm.

[0043] Step 2: preparing carbon nanotube-magnetic nanoparticle composite fibers, wherein the specific components include 85-95 parts of N,N-dimethylformamide, 5-15 parts of carbon nanotubes, and 5-15 parts of magnetic nanoparticles.

[0044] Furthermore, the mixture was heated to 50°C at room temperature, a rotation speed of 350 rpm / min, a power of 100 W, and mixed for 1 h.

[0045] Furthermore, the mass concentration of the mixed solution is 5-15%, the spinning machine speed is 1000 rpm, and the temperature is 50-70°C;

[0046] Further, the fibers were spun and heated to 250° C. at a rate of 2-4° C. / min under a nitrogen atmosphere and maintained for 1-2 hours.

[0047] Step 3: SiC surface treatment: average SiC particle size 1-5 μm, 2-3 parts of 3-aminopropyltriethoxysilane, 20-40 parts of SiC powder, rotation speed 400 rpm, temperature 50-70°C, maintain for 1-2 hours.

[0048] Step 4: Mixing the composite fiber and SiC powder, 2-5 parts of composite fiber, 5-15 parts of SiC powder, 1-5 parts of polyvinyl pyrrolidone, ball mill speed of 300 rpm, time for 2 hours.

[0049] Step 5: Place the SiC composite material and binder into the corresponding position of the binder jet printer, slice it according to the required model, and import the slice file into the device for molding.

[0050] Step 6: After molding is completed, place the molding cylinder in an oven at 150-200℃ for 2 hours to complete the curing.

[0051] Step 7: Take out the SiC parts and clean them to remove the loose powder.

[0052] Step 8: Place the SiC part in a degreasing furnace for degreasing, heat it to 400-600°C at a heating rate of 5-10°C / min, keep it at that temperature for 2 hours, and cool it with the furnace.

[0053] Step nine: heat treatment, sintering at 1550°C in an Ar atmosphere and keeping warm for 1 hour.

[0054] Step 10: After the SiC sample is taken out, mechanical properties, magnetic properties, and thermal properties tests are performed.

[0055] For a better understanding of the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as limiting the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above invention content are also considered to fall within the scope of protection of the present invention.

[0056] Example 1

[0057] Step 1: First, design the 3D model of the SiC part, cut it into a CLI format file using slicing software, and import it into the binder jet printer.

[0058] Step 2: Composite slurry preparation

[0059] 1. Material pretreatment:

[0060] Weigh 5 g of multi-walled carbon nanotubes (diameter 10-20 nm, length 1-5 μm) and 5 g of ferrite magnetic nanoparticles (diameter 5-10 nm), and place them in a vacuum drying oven under nitrogen protection (temperature 60°C, time 2 hours) to remove surface moisture;

[0061] N,N-dimethylformamide (DMF, 85 g) was added to a reactor equipped with a magnetic stirrer, the stirrer was started (initial speed 350 rpm), and the heating mantle power was set to 100 W;

[0062] 2. Dispersion mixing:

[0063] Slowly add carbon nanotubes into DMF, increase the speed to 500 rpm after complete soaking, and heat to 50°C and stir constantly for 1 hour;

[0064] Add ferrite particles in sequence and continue stirring for 30 minutes until the mixture is evenly mixed;

[0065] 3. Slurry filtration: Use a 0.45 μm filter membrane to vacuum filter (pressure 0.1 MPa) to remove undispersed particles and obtain a uniform slurry with a viscosity of 5000 ± 500 mPa·s.

[0066] Step 3: Continuous fiber spinning preparation

[0067] 1. Equipment debugging: Pour the composite slurry into the barrel of the electrospinning machine, set the distance between the needle and the receiving roller to 15 cm, and the receiving roller speed to 1000 rpm;

[0068] 2. Process control:

[0069] High-purity nitrogen (purity ≥ 99.999%) was introduced to exclude oxygen, the initial temperature was set at 60°C, the voltage was 15 kV, and the temperature was programmed to 250°C at a rate of 2°C / min;

[0070] Maintain the temperature at 250°C for 2 hours to allow the solvent to evaporate completely and complete fiber cross-linking;

[0071] 3. Fiber collection: The receiving roller automatically winds the fiber, and the fiber diameter is monitored in real time by a laser diameter detector (target range 200-500nm). The heating system is turned off after spinning is completed.

[0072] Step 4: SiC powder surface modification

[0073] 1. Coupling agent preparation: Weigh 3-aminopropyltriethoxysilane (KH550, 2g) and dissolve it in anhydrous ethanol (98g), stir well and let it stand for 30 minutes;

[0074] 2. Mixed modification:

[0075] SiC powder (20 g, particle size 1-5 μm) was added to a high-speed mixer, the stirrer was started (speed 400 rpm), and the silane ethanol solution was sprayed through an atomizing nozzle;

[0076] Maintain the temperature at 60°C and mix for 2 hours to allow the silane to fully hydrolyze and react with the hydroxyl groups on the SiC surface;

[0077] 3. Drying treatment: The modified powder was transferred to a vacuum oven (temperature 80°C, vacuum degree ≤10Pa) and dried for 4 hours to obtain amino SiC powder.

[0078] Step 5: Composite material 3D printing

[0079] 1. Slurry loading: Add the composite fiber (2 g), dried SiC powder (5 g), and polyvinyl pyrrolidone (PVP, 2 g) into the hopper of a twin-screw extruder and pre-mix for 2 minutes at a screw speed of 300 rpm.

[0080] 2. Printing process:

[0081] The powder thickness is 0.1mm on the printing platform, the nozzle temperature is set to 80℃, and the binder (ethanol-based) is sprayed layer by layer. After each layer is sprayed, the scraper is used to compact it.

[0082] After printing is completed, the molded part is transferred to an oven and heat treated at 180°C for 2 hours to remove residual solvent;

[0083] 3. Post-curing: After cooling naturally to room temperature, use a contact angle meter (water drop contact angle ≤ 45°) to verify the SiC powder modification effect.

[0084] The SiC parts were taken out and cleaned, and the floating powder was cleaned. They were placed in a degreasing furnace for degreasing. The heating rate was 5°C / min, heated to 600°C, and kept warm for 2 hours. Then they were placed in an Ar atmosphere sintering furnace for reaction sintering. The sintering temperature was 1550°C, the heating rate was 5°C / min, and kept warm for 1 hour. The final product was formed by cooling in the furnace.

[0085] Mechanical, electromagnetic and thermal performance tests were carried out respectively.

[0086] Mechanical properties test: The specimens were stretched using a UTM-5000 universal testing machine (rate 1 mm / min). The tensile strength was calculated using the formula σ = F / A.

[0087] Electromagnetic performance test: The conductivity was measured using an RTS-8 four-probe instrument (25°C), and the saturation magnetization was measured using a VSM (magnetic field strength of 1.5 T).

[0088] Comparative sample: pure SiC powder compression molding (100MPa, sintered at 1400℃), tensile strength 495MPa, thermal conductivity 12W / (m·K).

[0089] Performance improvement: tensile strength +15% (570MPavs 495MPa), thermal conductivity +67% (20W / (m·K) vs 12W / (m·K)).

[0090] Example 2

[0091] Step 1: First, design the 3D model of the SiC part, cut it into a CLI format file using slicing software, and import it into the binder jet printer.

[0092] Step 2: Composite slurry preparation

[0093] 1. Material pretreatment:

[0094] Weigh 5 g of multi-walled carbon nanotubes (diameter 10-20 nm, length 1-5 μm) and 10 g of ferrite magnetic nanoparticles (diameter 5-10 nm), and place them in a vacuum drying oven under nitrogen protection (temperature 60°C, time 2 hours) to remove surface moisture;

[0095] N,N-dimethylformamide (DMF, 85 g) was added to a reactor equipped with a magnetic stirrer, the stirrer was started (initial speed 350 rpm), and the heating mantle power was set to 100 W;

[0096] 2. Dispersion mixing:

[0097] Slowly add carbon nanotubes into DMF, increase the speed to 500 rpm after complete soaking, and heat to 50°C and stir constantly for 1 hour;

[0098] Add ferrite particles in sequence and continue stirring for 30 minutes until the mixture is evenly mixed;

[0099] 3. Slurry filtration: Use a 0.45 μm filter membrane to vacuum filter (pressure 0.1 MPa) to remove undispersed particles and obtain a uniform slurry with a viscosity of 5000 ± 500 mPa·s.

[0100] Step 3: Continuous fiber spinning preparation

[0101] 1. Equipment debugging: Pour the composite slurry into the barrel of the electrospinning machine, set the distance between the needle and the receiving roller to 15 cm, and the receiving roller speed to 1000 rpm;

[0102] 2. Process control:

[0103] High-purity nitrogen (purity ≥ 99.999%) was introduced to exclude oxygen, the initial temperature was set at 60°C, the voltage was 15 kV, and the temperature was programmed to 250°C at a rate of 2°C / min;

[0104] Maintain the temperature at 250°C for 2 hours to allow the solvent to evaporate completely and complete fiber cross-linking;

[0105] 3. Fiber collection: The receiving roller automatically winds the fiber, and the fiber diameter is monitored in real time by a laser diameter detector (target range 200-500nm). The heating system is turned off after spinning is completed.

[0106] Step 4: SiC powder surface modification

[0107] 1. Coupling agent preparation: Weigh 3-aminopropyltriethoxysilane (KH550, 2g) and dissolve it in anhydrous ethanol (98g), stir well and let it stand for 30 minutes;

[0108] 2. Mixed modification:

[0109] SiC powder (20 g, particle size 1-5 μm) was added to a high-speed mixer, the stirrer was started (speed 400 rpm), and the silane ethanol solution was sprayed through an atomizing nozzle;

[0110] Maintain the temperature at 60°C and mix for 2 hours to allow the silane to fully hydrolyze and react with the hydroxyl groups on the SiC surface;

[0111] 3. Drying treatment: The modified powder was transferred to a vacuum oven (temperature 80°C, vacuum degree ≤10Pa) and dried for 4 hours to obtain amino SiC powder.

[0112] Step 5: Composite material 3D printing

[0113] 1. Slurry loading: Add the composite fiber (3 g), dried SiC powder (5 g), and polyvinyl pyrrolidone (PVP, 2 g) into the hopper of a twin-screw extruder and pre-mix for 2 minutes at a screw speed of 300 rpm.

[0114] 2. Printing process:

[0115] The powder thickness is 0.1mm on the printing platform, the nozzle temperature is set to 80℃, and the binder (ethanol-based) is sprayed layer by layer. After each layer is sprayed, the scraper is used to compact it.

[0116] After printing is completed, the molded part is transferred to an oven and heat treated at 180°C for 2 hours to remove residual solvent;

[0117] 3. Post-curing: After cooling naturally to room temperature, use a contact angle meter (water drop contact angle ≤ 45°) to verify the SiC powder modification effect.

[0118] The SiC parts were taken out and cleaned, and the floating powder was cleaned. They were placed in a degreasing furnace for degreasing. The heating rate was 5°C / min, heated to 600°C, and kept warm for 2 hours. Then they were placed in an Ar atmosphere sintering furnace for reaction sintering. The sintering temperature was 1550°C, the heating rate was 5°C / min, and kept warm for 1 hour. The final product was formed by cooling in the furnace.

[0119] Mechanical, electromagnetic and thermal performance tests were carried out respectively.

[0120] Mechanical properties test: The specimens were stretched using a UTM-5000 universal testing machine (rate 1 mm / min). The tensile strength was calculated using the formula σ = F / A.

[0121] Electromagnetic performance test: The conductivity was measured using an RTS-8 four-probe instrument (25°C), and the saturation magnetization was measured using a VSM (magnetic field strength of 1.5 T).

[0122] Comparative sample: pure SiC powder compression molding (100MPa, sintered at 1400℃), tensile strength 495MPa, thermal conductivity 12W / (m·K).

[0123] Performance improvement: tensile strength +17% (580MPavs 495MPa), thermal conductivity +83% (22W / (m·K) vs 12W / (m·K)).

[0124] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A carbon nanotube composite fiber with magnetic nanoparticles attached to the surface, characterized in that: The method is prepared by composite spinning of multi-walled carbon nanotubes and ferrite magnetic nanoparticles; The multi-walled carbon nanotubes have a diameter of 10-20 nm and a length of 1-5 μm; The diameter of the ferrite magnetic nanoparticles is 5-10 nm.

2. A method for preparing a carbon nanotube composite fiber with magnetic nanoparticles attached to the surface as claimed in claim 1, characterized in that: The method specifically comprises the following steps: Step 1: Select multi-walled carbon nanotubes with a diameter of 10-20 nm and a length of 1-5 μm, and select ferrite magnetic nanoparticles with a diameter of 5-10 nm; Step 2: Spinning to prepare carbon nanotube-magnetic nanoparticle composite fibers, the specific components of which include 85-95 parts of N,N-dimethylformamide, 5-15 parts of multi-walled carbon nanotubes, and 5-15 parts of ferrite magnetic nanoparticles.

3. The method for preparing carbon nanotube composite fibers with magnetic nanoparticles attached to the surface according to claim 2, characterized in that: The carbon nanotube-magnetic nanoparticle composite fibers are prepared by mixing N,N-dimethylformamide, multi-walled carbon nanotubes and ferrite magnetic nanoparticles and spinning the mixture. The mass concentration of the mixed solution is 5-15%, the rotation speed of the spinning machine is 1000 rpm, and the temperature is 50-70°C.

4. The method for preparing carbon nanotube composite fibers with magnetic nanoparticles attached to the surface according to claim 2, characterized in that: The fibers were spun and heated to 250°C at a rate of 2-4°C / min under a nitrogen atmosphere and maintained for 1-2 hours.

5. Use of the carbon nanotube composite fiber with magnetic nanoparticles attached to the surface as claimed in claim 1 in enhancing SiC powder 3D printing.

6. The use according to claim 5, characterized in that The carbon nanotube composite fiber with magnetic nanoparticles attached to the surface is mixed with the surface-treated SiC powder, and then placed in a 3D printer and inkjet bonded with a prepared adhesive. The SiC part is then cured and strengthened, degreased after powder cleaning, and sintered by hot isostatic pressing.

7. The use according to claim 6, characterized in that The SiC powder surface treatment operation is as follows: Mix 20-40 parts of SiC powder with an average particle size of 1-5 μm and 2-3 parts of 3-aminopropyltriethoxysilane at 50° C.-70° C. for 1-2 hours.

8. The use according to claim 6, characterized in that The operation of mixing the composite fiber and the surface-treated SiC powder is as follows: 2-5 parts of composite fibers, 5-15 parts of SiC powder and 1-5 parts of polyvinyl pyrrolidone are ball-milled for 2 hours.

9. The use according to claim 6, characterized in that The curing temperature is 150-200°C, and the curing time is 2 hours. The degreasing parameters are as follows: Place the solidified SiC parts into a degreasing furnace for degreasing. Heat the parts to 400-600°C at a heating rate of 5-10°C / min, keep the temperature for 2 hours, and cool them down in the furnace.

10. The use according to claim 6, characterized in that The hot isostatic pressing sintering parameters are as follows: Sintered at 1550℃ in Ar atmosphere and kept warm for 1 hour.

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